مجله میکروبیولوژی کاربردی در صنایع غذایی
سال هشتم شماره 3 (پاییز 1401)

Bacteriocins are generally defined as peptides or proteins ribosomal synthesized by bacteria that inhibit or kill other microorganisms. Nowadays, bacteriocin industry as natural preservatives have substantially grown replacing the role of chemical preservatives in enhancing shelf-life and safety of food. The progress in bacteriocin study has been supported by the emerging of consumer demand on the applications of natural food preservatives. In this study, Lactobacillus helveticus were identified using the 16S rRNA gene sequencing method. The antimicrobial activity of the neutralized supernatant of Lactobacillus helveticus against some pathogenic microorganisms was investigated. Then, the different properties of this bacteriocin compound, such as its protein nature, heat and pH resistance, as well as the storage temperature on its stability, were examined. In this study, the supernatant of L. helveticus, showed antimicrobial activity against 7 pathogenic bacteria with 8.5-18.7 mm diameter in inhibition zone. The bacteriocin produced by L. helveticus was completely sensitive to proteinase K, α-chymotrypsin, protease, and trypsin; however, after exposure to pepsin, the activity was reduced by about 41% for Staphylococcus aureus and about 30% for Micrococcus luteus. Supernatants containing bacteriocin were resistant to different temperatures as well as pHs 2 to 11. Also, the best temperature for storing the studied bacteriocin was -80 oC for 1 month. The ability of bacteriocin produced by L. helveticus to inhibit growth of various pathogens as well as high stability to pH and temperature can be introduced it as a natural preservative.

Beta-glucan composite is a dietary fiber and has beneficial health effects that can be used as a prebiotic and fat replacer in the manufacture of dietary products such as low-fat yogurt.  The purpose of this research is to use beta-glucan exopolysaccharide in amounts of 0.1, 0.2, 0.3 and 0.4% (w/w) in the production of low-fat shaped sheep yogurt. And also, physicochemical (pH, % acidity, % total solids) and survival of starter cultures of treatments were determined during 21 days of storage period. Experiments were performed in a factorial form in a completely randomized design with the software of SPSS 16.0. Parallel to decreasing in pH, the acidity of all samples were increased significantly (p<0.05). The beta glucan concentration did not have significant effect on total solid amounts (p>0.05). Increase of beta glucan levels in yogurt formulation led to decrease syneresis however, the viscosity was increased. During storage, viscosity significantly was increased (p<0.05), but syneresis of all samples was decreased except for control sample. The concentration of beta glucan had not significantly effect on survival rate of both starter bacteria(p>0.05).  Finally, it concluded that beta glucan was the best fat replacer and could be used in formulation of yogurt with sheep milk. Addition of beta glucan at 0.2 and 0.3% levels had a good potential for being used as a stabilizer in yogurt formulation. The sample containing 0.3% beta glucan can be introduce as the best treatment.

Cold plasma is a non-thermal technology and a suitable alternative to conventional thermal methods used in the food industry, which, with its antimicrobial properties, increases the shelf life of food products without negatively affecting their quality. The purpose of this research is to investigate the physicochemical, microbial and sensory properties of red grape juice pasteurized by cold plasma method (under plasma irradiation with voltage of 20, 40 and 60 kV for a period of 1, 2, 3 and 4 min and air gas) and compare it with thermal pasteurization (95°C for 5 seconds). The results showed that the effect of treatment on physicochemical properties (acidity, pH and Brix), bioactive compounds (anthocyanin, total phenol and vitamin C), color properties (components a*, b* and L*), microbial load (mold and yeast, aerobic bacteria and coliform) and sensory characteristics (taste, smell and overall acceptance) of red grape juice pasteurized by cold plasma method was significant (p≤0.05) so that with increasing amount voltage from 20 to 60 kv and time from 1 to 4 min, in grape juice pasteurized by cold plasma method, the amount of acidity, brix, color components a* and b* increased significantly (p≤0.05) and the amount pH, bioactive compounds (anthocyanin, total phenol and vitamin C), the amount of color of L* component, the amount of microbial load (mold and yeast, aerobic bacteria and coliform) decreased significantly (p≤0.05). Also, by increasing the time from 1 to 4 min, the smell score and overall acceptance decreased, and by increasing the voltage from 20 to 60 kV and the time from 1 to 4 min, the taste score decreased. Since the physicochemical, color, microbial and sensory changes of red grape juice pasteurized by cold plasma method in the conditions of 40 kv, 4 min time and air gas were less than thermal pasteurization method and more acceptable for consumption, it was introduced as a superior treatment.

Seafood due to high water activity, neutral pH, high ratio of free amino acids are involved in microbial spoilage and consequently their quality and shelf life are reduced. In this study, the preservative effect of powdered ice in four forms of pure and combined with Sargassum tenerrimmum algae extract, aeromycin antibiotic and nisin-z on increasing the shelf life of Vanami shrimp during 12 days of storage in refrigeration was evaluated. Shrimps were prepared from Gomishan Breeding Center and all experiments were performed in the Faculty of Fisheries, Gorgan University of Agricultural Sciences and Natural Resources. Shrimp covered with ice were evaluated every 3 days by measuring the microbiological characteristics of Common spoilage bacteria (CSB), Psychrophilic bacteria (PSB), Lactic acid bacteria (LAB) and Enterobacteriaceae (EB). The fastest deterioration trend of all bacterial analyzes was observed in the control and algae extract samples and these two treatments showed the highest increase at the end of storage time (p <0.05). Ice containing nisin z had a relatively good preservative effect on CSB, LAB, and PSB, but was ineffective against EB. The antibiotic aeromycin showed a significant inhibitory effect, so that the growth of EB and LAB during the storage time was close to zero. CSB and PSB had also similar conditions in this treatment and even decreased during storage.

This study was done to evaluate the effect of using different levels of Portulaca Oleracea seed on growth performance, immune system and some blood parameters of broiler chickens. A total of 160 one day old broiler chicks (Ross 308 commercial strain) was used in a completely randomized design with 4 treatments, 4 replicates and 10 chicks in each replicate. Experimental diets include Portulaca Oleracea seed at the levels of 0, 2, 5/2, 5 and 5/7 percent. To evaluate the humoral immune system, 1 ml of SRBC (%10) was injected to 2 chicks in each replicate and blood samples collected from wing vein on 35, 42 d. Birds vaccinated against bronchitis, Newcastle and Gambaro diseases. The blood samples of 42 d were used for measuring blood parameters. Body organs were studied as percentage of body weight on 42 d. The results showed that Portulaca Oleracea seed increased body weight and feed intake of broiler chickens at growth, finisher and whole period of rearing (P<0.05). There was no difference among birds IgY titer. Feed conversion ratio improved with Portulaca Oleracea seed at the level of 2/5 percent in all experimental periods (P<0.05). The weight of bursa of fabricius and other body organs was not different in all groups at 42 d. Using different levels of Portulaca Oleracea seed in experimental diets had not significant effect on antibody titer against SRBC, blood hematocrit, triglyceride, ALP, AST, ALT enzymes and blood calcium, but it increased blood cholesterol concentration (P<0.05).

The determination of bovine tuberculosis is made with different tests and with certain limitations. Antigenic proteins can be extracted from Mycobacterium bovis culture that can improve the sensitivity and specificity of diagnostic tests. One of the targets of this study is to design an indirect ELISA. For this reason, purified Mycobacterium bovis AN5 antigen were utilized to distinguish bovine tuberculosis. Another goal is to review and compare the results of the system designed to Interferon-ɣ (IFN-ɣ) assay. Mycobacterium bovis AN5 antigens were isolated and purified. The selected antigen was then used to design the indirect ELISA system. The sera of 230 cows from different farms were tested with designed ELISA. Their results were at that point compared with interferon-gamma test as a corroborative diagnostic test. Correlation and independent study between variables were performed by Pearson and T test. The sensitivity and specificity of the designed indirect ELISA system were 77.8% and 80.7%, respectively. The p value for Pearson and T test was zero percent. Noteworthy lightweight antigens were purified that might analyze the disease. Due to the high sensitivity and specificity gotten, the ELISA system outlined for starting screening within the diagnosis of bovine tuberculosis.